1. Field of the Invention
Embodiments described herein relate generally to a holding mechanism and an imaging device comprising this holding mechanism. The holding mechanism positions and fixes a movable body at a predetermined position in equipment which moves the movable body in a plane direction by the use of an electromagnetic motor.
2. Description of the Related Art
An electrically driven stage capable of moving in X-axis and Y-axis directions and rotating around a Z-axis (i.e. moving in an XY plane) has heretofore been in use in various places, wherein the X-axis, Y-axis, and Z-axis are three axes of a rectangular coordinate system.
A known concrete example is a shake correction mechanism in a camera. The shake correction mechanism uses shake detection means such as an angular velocity sensor and an acceleration sensor to detect shake vibrations in a pitch direction (rotational direction around the X-axis extending to right and left) of the camera, shake vibrations in a yaw direction (rotational direction around the Y-axis extending up and down) of the camera, shake vibrations in the X-direction (right-and-left direction), shake vibrations in the Y-direction (up-and-down direction), and rotational shake vibrations around the Z-axis (back-and-forth direction). In accordance with detected shake signals, the shake correction mechanism displaces a part of an imaging optical system or an image pickup device (hereinafter referred to as a drive target) in a shake-counteracting direction along a plane that intersects at right angles with an imaging optical axis, and thereby corrects the shake of a figure on an imaging surface of the image pickup device.
This shake correction mechanism has drive means for horizontally and vertically moving the drive target along a plane that intersects at right angles with the imaging optical axis to correct a hand shake. When operating to follow the hand shake, the drive means needs to accurately drive (finely drive) the drive target. The drive means also needs to correctly position the drive target relative to the optical axis of the camera. High drive force is required for the drive means to overcome the gravity of the drive target and obtain acceleration necessary for control.
In the meantime, when no shake correction is made, the drive target needs to be fixed at a home position. In this case, it is preferable to have self-holding performance so that the position of the drive target is held even when the power is off. It is appreciated that such a fixing mechanism is required to be an uncomplicated, small, and low-cost mechanism.
For example, a device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2008-129326 uses frictional force to hold, between two yoke plates, a substrate holding an image pickup device, and drives the substrate by a voice coil motor to correct a hand shake.
Jpn. Pat. Appln. KOKAI Publication No. 2010-282028 has disclosed a lens unit which uses a piezoelectric element to fix and unfix, relative to a stator, a movable element holding a lens.
When a method that uses frictional force between members to hold a movable body is used, high energy is needed to overcome the frictional force in order to move the movable body, and the output of a driver deteriorates. This problem becomes more serious particularly when the frictional force is increased to increase the holding force of the movable body, and it becomes difficult to accurately position the movable body at a desired position.
When the method that uses the piezoelectric element to fix and unfix the movable body is used, the application of electricity to the piezoelectric element needs to be continued, for example, to keep the movable body unfixed, which leads to increased electric power consumption.
An object of the present invention is to solve the problems associated with the above-mentioned conventional techniques, and provide a holding mechanism having a simple and low-cost configuration that can mechanically position and hold a movable body, and an imaging device comprising this holding mechanism.
Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.